Alcohol is accepted as legally relevant regarding mens rea, automatism, insanity, diminished capacity, and provocation. The paper examines such assumptions made by judges and legal academics and traces them back to medical and ideological roots in the 19th century. These assumptions are contrasted with scientific evidence on the relationship between psychoactive drug use and violent behavior, recklessness, intention, cognitive ability, memory, automatism, and insanity. The discussion reveals important discrepancies between empirical evidence and legal assumptions about intoxication. A review of relevant cases illustrates that the facts in such cases are consistent with scientific findings, but often inconsistent with legal decisions. In analyzing the role of medical testimony on intoxication in the criminal court, the paper concludes that it does not serve the interests of justice. Minimizing the inclusion of medical testimony and adopting a per mens rea test for criminal liability is advocated. 166 footnotes.